X-ray determination of threading dislocation densities in GaN/Al2O3(0001) films grown by metalorganic vapor phase epitaxy

Abstract

Densities of a-and aþc-type threading dislocations for a series of GaN films grown in different modes by metalorganic vapor phase epitaxy are determined from the x-ray diffraction profiles in skew geometry. The reciprocal space maps are also studied. Theory of x-ray scattering from crystals with dislocations is extended in order to take into account contribution from both threading and misfit dislocations. The broadening of the reciprocal space maps along the surface normal and the rotation of the intensity distribution ellipse is attributed to misfit dislocations at the interface. We find that the presence of a sharp AlN/GaN interface leads to an ordering of misfit dislocations and reduces strain inhomogeneity in GaN films. V

Oxygen vacancy-assisted recovery process for increasing electron mobility in n-type BaSnO3 epitaxial thin films

“…Therefore, the type of TD in the epitaxial layers affects the direction of lattice distortion, so the RSM FWHMs change asymmetrically. For example, in GaN epitaxial films with a high density of TDs, edge-type TDs widen the in-plane FWHMs and screw-type TDs widen the out-ofplane FWHMs [30][31][32][33] . Likewise, the observed reduction in the in-plane FWHMs in our LBSO epitaxial films should be related to a decrease in the edge-type N TD rather than the screwtype N TD after the H 2 treatment.…”

Characterization of dislocations in germanium layers grown on (011)- and (111)-oriented silicon by coplanar and noncoplanar X-ray diffraction

“…Because of this fact we will neglect fine effects due to modification of the displacement fields related to the presence of the boundary and will use the solution for an infinite medium. In papers by Kopp and co-workers (Kopp, Kaganer, Baidakova et al, 2014;Kopp, Kaganer, Jenichen & Brandt, 2014) the effect of boundary terms on the X-ray diffraction profile was accounted for using the direct assumption-free Monte Carlo approach and it was shown to be subtle. For the mentioned reasons we will use the displacement fields for an infinite medium,…”

“…To do this one has to transform both quantities to the same coordinate system. This can be easily done for the particular cases described by Kaganer et al (1997) and Kopp, Kaganer, Baidakova et al (2014), but for a general case one would need a universal recipe. In order to provide it, let us consider the crystallographic coordinate system C:…”

“…A theoretical approach for calculation of the diffracted X-ray intensity distribution from epitaxial layers possessing dislocations was developed by Kaganer et al (1997) and successfully applied to a number of systems (Kaganer et al, 2006b;Benediktovich et al, 2011;Kopp, Kaganer, Baidakova et al, 2014). The peak shape is sensitive to the reflection used, the measurement geometry, the type of dislocations, their density and their degree of correlation.…”

Dislocation density and strain-relaxation in Ge 1−x Sn x layers grown on Ge/Si (0 0 1) by low-temperature molecular beam epitaxy

“…Here, we study the molecular-beamepitaxy (MBE)-growth of Ge1-xSnx layers on Ge/Si(001) substrates and investigate the threading dislocation densities (TDD) in these layers, by the approach developed by Kaganer et al [16,17]. We demonstrate that this high-resolution-X-ray-diffraction (HRXRD)-based technique, which has been successfully used to estimate dislocation densities in GaN [18][19][20] and SiGe [21][22][23] in previous works, also provides very reliable estimate of the same, for large area Ge1-xSnx epilayers. We observe that the relaxation of the Ge1-xSnx epilayers is predominantly driven by dislocations threading from the underlying Ge buffer layers.…”